C# Threading: Mutual exclusion (via Monitor Class)

Observe the following faulty snippet from this post:

 
using System;
using System.Threading;
using System.IO;
 
class Program
{
    static void Main(string[] args)
    {
        for (int i = 0; i < 3; i++)
        {
            Thread thread = new Thread(new ThreadStart(ThreadMain));
            thread.Name = String.Concat("Thread - ", i);
            thread.Start();
        }
    }
 
    static void ThreadMain()
    {
        // Simulate Some work
        Thread.Sleep(500);
 
        // Access a shared resource / critical section
        WriteToFile();
    }
 
    static void WriteToFile()
    {
        String ThreadName = Thread.CurrentThread.Name;
        Console.WriteLine("{0} using resource", ThreadName);
 
        try
        {
            using (StreamWriter sw = new StreamWriter("1.txt", true))
            {
                sw.WriteLine(ThreadName);
            }
        }
        catch (Exception ex)
        {
            Console.WriteLine(ex.Message);
        }
    }
}
 

 
static object locker = new object();
 
static void WriteToFile()
{
    String ThreadName = Thread.CurrentThread.Name;
    Console.WriteLine("{0} using resource", ThreadName);
 
    Monitor.Enter(locker);
    try
    {
        using (StreamWriter sw = new StreamWriter("1.txt", true))
        {
            sw.WriteLine(ThreadName);
        }
    }
    catch (Exception ex)
    {
        Console.WriteLine(ex.Message);
    }
    finally
    {
	Monitor.Exit(locker);
	Console.WriteLine("{0} releasing resource", ThreadName);
    }
}
 

 
static object locker = new object();
 
static void WriteToFile()
{
    String ThreadName = Thread.CurrentThread.Name;
    Console.WriteLine("{0} using resource", ThreadName);
 
    lock (locker)
    {
        try
        {
            using (StreamWriter sw = new StreamWriter("1.txt", true))
            {
                sw.WriteLine(ThreadName);
            }
        }
        catch (Exception ex)
        {
            Console.WriteLine(ex.Message);
        }
    }
}
 

 
if (Monitor.TryEnter(locker, 500))
{
    try
    {
        Console.WriteLine("Lock Achieved");
        Thread.Sleep(1000); // Simulate work
    }
    catch
    {
    }
    finally
    {
        Monitor.Exit(locker);
    }
}
else
{
    Console.WriteLine("Lock Failed");
}
 

Book Review: PHP 6 and MySQL 5 for Dynamic Web Sites

This book has actually been on my bookshelf for quite a while, I bought it a few months before the promised release of PHP 6 in 2008 (which never happend).

Unfortunately I didn't realise at the time that the author made a typo when he gave the book its title, since the book primarily focuses on functionality thats been around since PHP 4 - with some PHP 5 examples (e.g. mysqli extension).

PHP 6 is more like a side note in this book.

I can however imagine that it is quite difficult to write a book about a product that strictly speaking doesn't actually exist - so I will cut the author some slack. (apparently a lot, if not most of the suggested PHP 6 functionality are currently available within PHP 5.3)

Looking at the actual content, the table of contents reveals that this book is intended for beginners - so don't expect finding any nuclear bomb blueprints in this book (incidently).

I personally feel that the structure of this book is a bit illogical, for example in Chapter 3 on page 89 - 91 the author crudely explains how to create what he calls a sticky form (persisting selected/entered data in a form).

In order to get a less mediocre understanding of forms, the reader needs to advance to Chapter 8 on page 243 - 248 where they learn about magic quotes (which potentially messed up their sticky form back in Chapter 3) and SQL injection (which potentially messed up their database if they had one).

Another crucial part that relates to the sticky form only really gets discussed in Chapter 12 - form/data validation, html encoding (which potentially breaks their page layout) etc.

In my opinion it would have been more logical to explain all of these concepts together - since they are pretty much directly related to one another.

But then again thats my own preferences I guess, at least the book contains these concepts.

All in all I dont feel its a bad book (for a beginner) - definitely not what I expected or had in mind when I purchased it (I was expecting more of a PHP 6 primer) - don't judge a book by its title.

Additional Reading:

Have a look at the Errata if you're planning to buy this book, there is quite a number of little mistakes.

Also be sure to visit the author's (Larry Ullman) website www.dmcinsights.com